1. Field of the Invention
The present invention relates to a display device and a method for manufacturing the same; more particularly, the present invention relates to a high color expression display device and a method for manufacturing the same.
2. Description of the Prior Art
Display panels and panel display devices using the display panels have become the mainstream display devices. For example, various panel displays, home flat televisions, panel monitors of personal computers and laptop computers, and display screens of mobile phones and cameras are products widely using display panels. Particularly, the market demand for liquid crystal display devices largely increases in recent years. In order to meet the function and appearance requirements of liquid crystal displays, the design of backlight modules used in liquid crystal display devices is also diverse.
In conventional, the backlight module usually uses tube lamps as the backlight source. Light emitted from the tube lamp can achieve a certain level of color rendering and color saturation. However, since the tube lamp occupies a larger space, the backlight module equipped with the tube lamp accordingly has a larger volume. Additionally, the tube lamp consumes more power resulting in low usable time for the entire system. In order to address the above problems, some backlight modules use white light emitting diodes (LEDs) as the light source. The white LED is advantageous in environmental protection, low power consumption, and small volume. However, the color expression and color saturation of the white LED still cannot match up those of the tube lamp. For example, the white LED made of a blue LED chip with yellow green phosphors usually generates small energy in the red light range causing color shift in the generated white light.
Additionally, due to material properties and production limitations of the white LED, the availability of white LEDs is restricted. As shown in FIG. 1, due to various limitations, the available or suitable white LEDs are those having coordinates fallen into the area 10 (for example, in the CIE 1931 coordinate system). However, in consideration of color saturation and expression of other colors, the practical white LEDs may be those having coordinates fallen into the area 30. Since only half of white LEDs in the area 30 will meet the limitations defined in the area 10, the other half of white LEDs are not applicable which inevitably increases the production cost.
Furthermore, for the current white LED technology, when the NTSC saturation of the display module is greater than 60%, other than the difficulties in selecting or manufacturing white LEDs, the overall green color of the display module usually shifts to adversely affect the overall color expression. The “NTSC saturation” means a percentage expression of dividing the actual color area of primary colors of the display module by the standard color area of primary colors defined by the NTSC (National Television System Committee). As described above, the color shift problem occurred when the NTSC saturation is high is one of the major problems of using the white LED as the backlight source.